This invention generally relates to any electronically controllable motor and to systems, such as heating, ventilating and/or air conditioning (HVAC) systems having motors therein for driving indoor blowers and including a temperature sensor for regulating motor speed or torque.
Presently available motors, such as conventional brush-commutated DC motors, conveniently provide for changing operation speeds. However, there are disadvantages associated with these motors such as brush wear, electrical loss, noise and radio frequency interference caused by sparking between the brushes and the segmented commutator, and overall material cost of the motor. These disadvantages limit the applicability of such motors in many fields, including the refrigeration or HVAC fields. Electronically controlled motors, such as electronically commutated motors including brushless DC motors and permanent magnet motors with electronic commutation, have now been developed and generally are believed to have the advantageous characteristics of brush-commutated DC motors without many of the disadvantages thereof while also having other important advantages. Such electronically commutated motors are disclosed in, for instance, U.S. Pat. Nos. 4,015,182, 4,459,519, 4,642,537, 4,757,241 and 4,806,833, all of which are commonly assigned with the present application and the entire disclosures of which are incorporated herein by reference in their entirety.
Present motors have a variety of features and operational and system parameters which must be adjusted to optimize performance by providing a proper speed/torque characteristic for a particular application. Further, in many system applications, the speed/torque characteristics of the motors must be predictable and repeatable. In addition, it is desirable that motors be operable at the highest reasonably achievable efficiency consistent with mass production techniques. Known present variable speed motors cannot easily achieve this advantage because it has traditionally been impractical or too costly to minimize the variable effect on motor characteristics caused by manufacturing tolerances of the internal components of the motor. Present concepts and arrangements for adjusting a motor for different applications require circuit changes such as multiple variable resistors in the electronic control for the motor or permanent software changes in an electronic control microprocessor. Both of the aforementioned arrangements are disadvantageous because they require a unique model to be built for calibrating a system which cannot be easily changed and can be quite expensive.
In the specific case of HVAC systems, such systems may include a variety of backup heat ratings, operate in a variety of modes, have variable capacities and be installed in a variety of environments. Both the speed and torque of an electric motor, which affect air flow through the system, are affected by the aforementioned variables. Interfacing a control microprocessor with the necessary information to make these changes often requires complex assemblies, creates possible shock hazards and/or limits the number of available variations.
Although programmable motors offer numerous advantages over conventional, nonprogrammable motors, extensive laboratory testing and calibration by original equipment manufacturers is often required to develop the appropriate system characteristics. Constants are programmed into such motors to define the relationship between speed and torque versus air flow. Disadvantageously, tuning these constants can be time-consuming. Further, variations in blower wheels, cabinets, housings, and the like may change the system characteristics necessitating changes in the constants. Each set of constants corresponds to a new "model" which the motor must accommodate. For these reasons, an improved programmable motor is desired which readily accommodates changes in system characteristics to provide optimum and efficient air flow and reduced noise in the system.